The present invention relates to a fluid flow rate regulation device capable of fine flow rate regulation and an evacuation device for a sphygmomanometer whereby the air that is supplied to an armband can be evacuated with fixed speed, and to a sphygmomanometer of small power consumption, that is capable of miniaturization, and that is capable of measuring with high precision.
As shown in FIG. 8, a constructional example of a sphygmomanometer comprises: an armband 1 mounted so as to be wound on to an arm or neck or a finger etc. of a human body; a pump 2 that supplies compressed air to this armband 1; a pressure meter 3 that detects air pressure within this armband 1; an electrically-operated evacuation device 4 that evacuates the air within armband 1; and a microcomputer 5 that supplies air of fixed pressure into armband 1 by controlling operation of pump 2 in accordance with a detection signal from pressure meter 3 and that evacuates air with fixed speed from armband 1 by controlling the operation of electrically-operated evacuation device 4.
Conventionally, as shown in FIG. 9 and FIG. 10, electrically-operated evacuation device 4 comprises: a bobbin 6 having a through-hole 6a and with a coil 6b wound at its periphery; a practically U-shaped yoke 7 arranged so as to cover one end and the sides of this bobbin 6; a cover 8 that abuts the other end of bobbin 6 and is fixed in the open end of yoke 7, co-operating with this yoke 7 to form a magnetic path from the center of bobbin 6 to one end face and from the sides of bobbin 6 to the other end face; a movable element 9 comprising a magnetic element freely slidably mounted within a through-hole 6a of bobbin 6; a main valve body 10 mounted passing through this yoke 7 in a portion of yoke 7 covering one end of bobbin 6 and that is inserted from one end thereof into the through-hole 6a of bobbin 6 and is arranged facing movable element 9; a valve element 11 made of resilient material that effects opening/closing of an evacuation port 10a by contacting or being separated from this evacuation port 10a formed in main valve body 10, by sliding action of movable element 9, being mounted at the end of movable element 9 facing main valve body 10; and a resilient member 12 interposed between movable element 9 and main valve body 10 that biases movable element 9 in the direction away from main valve body 10.
The conventional electrically-operated evacuation device for a sphygmomanometer constructed in this way is arranged such that, by supplying drive current to coil 6b, movable element 9 is slid against the resilient force of resilient member 12 by the magnetic force which is then generated, causing valve element 11 that is mounted on this movable element 9 to be pressed against main valve body 10, thereby blocking its evacuation port 10a and such that the pressure within this armband 1 is raised to a fixed pressure by supplying a prescribed quantity of air to armband 1 by driving pump 2, after which pump 2 is stopped and [the supply of current] to coil 6b of electrically-operated evacuation device 4 is stopped, thereby causing movable element 9 to be slid in the direction away from main valve body 10 by the resilient force of resilient member 12, opening evacuation port 10a and allowing air to be evacuated from armband 1.
Also, it is arranged to keep the rate of evacuation constant by controlling the mode of current passage or stoppage thereof to coil 6b. 
However, in a conventional electrically-operated evacuation device for a sphygmomanometer constructed in this way, movable element 9 can move freely in the radial direction of bobbin 6; as a result this movable element 9 comes into contact with the inside wall of bobbin 6, generating a frictional force on sliding of movable element 9. There is therefore considerable hysteresis in the opening/closing drive of valve element 11 by microcomputer 5, resulting in poor accuracy of pressure reduction control of armband 1 and so imposing limitations on the precision of the sphygmomanometry.
Since this frictional resistance changes depending on the attitude of the electrically-operated evacuation device for a sphygmomanometer, there is also the inconvenience that the precision of the sphygmomanometry varies depending on the attitude in which the sphygmomanometer is arranged.
Also, in order to cause movable element 9 to slide in the direction such as to block evacuation portion 10a, it was necessary to generate in coil 6b sufficient attractive force to overcome the resilient force of resilient member 12 and the frictional resistance, so the drive current supplied to coil 6b became large, causing an increase in power consumption.
Also, movable element 9 being formed by a magnetic body, its weight is considerable and this also tends to increase the drive current.
Furthermore, although, in order to miniaturize the electrically-operated evacuation device for a sphygmomanometer it is necessary to make the number of turns of coil 6b small and the external diameter of bobbin 6 small, if the number of turns of coil 6b is made small, its attractive force becomes small, with the result that the large attractive force which is necessary to move movable element 9 as described above cannot be obtained.
Also, although it might be thought that miniaturization of the electrically-operated evacuation device for a sphygmomanometer could be achieved while maintaining the number of turns of coil 6b by reducing the weight of movable element 9 by making it smaller and employing an external diameter of small dimensions, making movable element 9 small reduces the attractive force on movable element 9 for the same magnetic flux density; this therefore tends to result in incomplete operation of the movable element 9 and so is not an effective remedy.
With the foregoing in view, it is an object of the present invention to provide a fluid flow rate regulation device capable of fine flow rate regulation and an evacuation device for a sphygmomanometer whereby the air that is supplied into an armband can be evacuated with a constant speed, and a sphygmomanometer whose power consumption is small, which can be made of small size, and which is capable of measurement with high accuracy.
A fluid flow rate regulation device according to a first invention for solving the above problem is provided comprising a fluid passage port and a valve element that effects opening/closure of this fluid passage port, in which the flow rate of fluid flowing through said fluid passage port is regulated by regulating the degree of opening/closure of this valve element wherein: fine irregularities are formed in said fluid passage port and/or valve element in at least a portion where the fluid passage port and valve element make contact.
Also, a second invention constituting an aspect of this first invention is provided wherein the portion in said fluid passage port and/or valve element where at least the fluid passage port and valve element make contact is constituted by a resilient member.
Also an evacuation device for a sphygmomanometer according to a third invention is provided whereby air that is fed into an armband comprised by the sphygmomanometer is gradually evacuated, comprising:
an evacuation port whereby the air that is fed into said armband is evacuated and a valve element that performs opening/closure of this evacuation port, wherein:
fine irregularities are formed on a portion in said evacuation port and/or valve element where at least the evacuation port and valve element make contact.
According to a fourth invention constituting an aspect of this third invention there is provided an evacuation device for a sphygmomanometer according to claim 3 wherein the portion in said evacuation port and/or valve element where at least the evacuation port and valve element make contact is constituted by a resilient member.
Also, an evacuation device for a sphygmomanometer according to a fifth invention is provided whereby air that is fed into an armband comprised by the sphygmomanometer is gradually evacuated, comprising:
a casing; a valve element that performs opening/closure of an aperture arranged in this casing; a cylindrical yoke provided with means for driving that drive opening/closure of this valve element, these means for driving being mounted within said casing; a core provided with a cylindrical part arranged concentrically within this yoke and a flange abutted by one end of said yoke; a magnet that forms magnetic flux in the radial direction and that is arranged within said yoke with a separation with respect to said core; a movable element provided through the cylindrical part of said core, with said valve element integrally mounted at one end thereof; coil arranged in the gap between said magnet and the yoke and fixed at one end of said movable element; and holding members interposed between both ends of said movable member and said casing and that holds said movable element and coil in non-contacting condition with respect to said core and yoke.
Furthermore, a sphygmomanometer according to a sixth invention is provided comprising:
an armband; a pump that supplies compressed air to this armband; a pressure meter that detects the air pressure within said armband; an evacuation device that evacuates the air within said armband 1; and a microcomputer that supplies air at constant pressure to said armband 1 by controlling the action of said pump in accordance with the detection signal from said pressure meter, and that evacuates air at a constant velocity from said armband by controlling the action of said evacuation device, wherein:
an evacuation device for a sphygmomanometer according to claim 3 to 5 is employed as said evacuation device.